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Plating Process

Written by Chuck. Posted in Plating

Copper Plating Through Holes

For plating through holes I use the solution available at Caswell Electroplating.

http://www.caswellplating.com/kits/copper.htm

Use the Bright Acid Copper Plating method, not the Flash Copper method.

I didn’t purchase the entire kit, but only the chemicals to make up the solution.

I mix the solution in a Snapware container. I use some J-Hooks from Lowes to hang the copper anode in the tank and to hang the board I am plating in the tank. I use an aquarium air stone for aeration and a Kapco Power Supply for the current. I do not use any heat, just standard room temperature.

It all works very well.

Solution

  • 1 Pack Copper Crystals (Makes 1.5 Gals)
  • 1 x 1.5oz Copper Brightener A
  • 1 x 4oz Copper Brightener B

I mix up ½ of the solution for my size Snapware container.

  • Pour 88 fl oz or 2.6 liters of distilled water into the tank. I actually use a 4 liter beaker for this mixing process but the tank will work.
  • Add ½ of the copper crystals (1.25 pounds).
  • Add 8 ounces or 236 mL of battery acid
  • Add .75 oz or 22 mL of the Copper Brightener part A.
  • Add 0.15 oz or 4.4 mL of Copper Brightener part B

I actually use a 10 mL syringe to measure the two parts of Copper Brightner and a small graduated cylinder to measure the battery acid. But you can convert the measurements to teaspoons and tablespoons and still get accurate results.

The Copper Brightener Part B is consumed by the system. So you need to occasionally add some small amounts. 2 mLs every 10 or so boards is sufficient. Technically you add 1 quart of Part B per 2000 amp hours. That’s .5 mL per hour or 1 mL every 5 boards.

Anodes

I have been using the 4x8 inch copper anodes and bandages available on the Caswell web site. I cut the anode to a length to fit into the tank, then drill two holes in it and mount it to plastic j-hooks using nylon machine screws. All available at Lowes. Then I wrap the bandwage around the anode and secure it with plastic zip ties. This prevents the solution from being trashed with small bits of copper as the anode disintegrates.

Plating

I found using a plating mask reduces the surface area to an area small enough to easily plate with this small tank.

Currently with this setup I plate for 6 minutes at 6 amps of current, then I flip the board on the Y-Axis and plate another 6 minutes at 6 amp. I’m getting perfect through hole plating.

Process

See the following areas for the complete process.

  1. Thoroughly clean the PCB
  2. Apply conductive ink
  3. Oven dry conductive ink
  4. Apply plating mask
  5. Produce the copper plating
  6. Remove the mask and clean the board
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Plating Step 1 -- Cleaning the PC Board

Written by Chuck. Posted in Plating

thumb_wash
The first step of the through hole plating process is the make sure the PC Board is clean.
We need to remove any protective coatings, grease, oil, dirt or tarnish.
I use a commercial abrasive cleaner for this step.
 
 
 
 
 
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Plating Step 2 -- Applying the Conductive Ink

Written by Chuck. Posted in Plating

The next step is to apply the conductive ink and coat the inside of the through holes.
Known in the industry as "holewall activation", most of the procedures encountered in the production of commercial printed circuits are fairly complex, requiring multiple process tanks, each with it's own control and maintenance requirements.
A method that is far more amenable to the needs of the PCB prototype involves the use of a low viscosity "ink" that has been specially formulated to form a high adhesion, high-conductivity coating on the inside wall of each through-hole.
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Plating Step 4 -- Preparing the mask

Written by Chuck. Posted in Plating

In progress
As far as I know I am the only one who uses a plating mask for through hole plating.  I started using this method because I was trying to plate PC Board in 3.5 liters of plating solution and it was very hard to get the amps and times down correctly.  With such a small bath -- I was getting incosistent results.
So I tried putting etchant resist mask on the PCB, which only left the through holes and via exposed to the plating solution.  This has been giving me consistentn plating results.
  • Laminating
  • Exposing
  • Developing